Check out our list of the 10 best NFL defenses of all time, and then see how our readers ranked their choices for the most dominating defensive unit. And be sure to vote in the poll to crown the No. 1 defense ever.

1. 1976 Pittsburgh Steelers
The Steelers defenses of the 1970s are legendary, but the 1976 unit was the best (slightly better than the '75 squad). Here's why: 28. That's how many points the Steel Curtain surrendered in the last nine games of the season. That's a total. As a result, Pittsburgh, which started the season 1-4, made it all the way to the AFC Championship Game, which they lost to the Raiders 24-7. (It's worth noting that Pittsburgh running backs Franco Harris and Rocky Bleier were both injured in that contest.)

The Bears had a very good offense in 1985, but it was Buddy Ryan's blitzing "46" defense that earned this team Page 2's honor of greatest NFL team of all-time. The Bears, with a D anchored by middle linebacker Mike Singletary (with superb assistance from tackles William "Refrigerator" Perry and Dan Hampton, outside linebackers Otis Wilson and Wilbur Marshall, and DE Richard Dent), went 15-1, holding seven opponents to fewer than 10 points.

The Bears showed their ultimate mettle in the playoffs. In the NFC divisional playoff, they shut out the Giants 21-0. The next week, they won the NFC championship by goose-egging the Rams 24-0. Then, in the Super Bowl, they held the Pats to a total of seven (7) yards rushing, helping to seal a 46-10 win.

"The Bears had a tremendous tactical advantage," said Bud Carson, the Steelers defensive coordinator from 1972 to 1977. "Teams that stayed in normal offensive formations got ripped apart. At that time, I had never seen anything like the advantage the Bears enjoyed. Buddy was reckless and crazy in a good way. He had so many blitzes. Defensive coordinators dream about doing what he did. He definitely had his moment in time."

3. 2000 Baltimore Ravens

Ray Lewis' Ravens roughed up the Giants in Super Bowl XXXV.

In the past quarter-century, only one defense has held opponents to fewer than 11 points per game. That team? Ray Lewis' Ravens. In 2000, Baltimore set NFL records for fewest points allowed (165) and fewest yards rushing allowed (970) in a 16-game schedule. In addition to Lewis, who eventually was named Super Bowl MVP, Baltimore's defense boasted safety Rod Woodson, who was named to the NFL's 75th Anniversary All-Time Team.

During the regular season, the Ravens shut out four opponents, then got better in the playoffs, allowing a total of only 23 points in four
games, including their 34-7 victory over the Giants in the Super Bowl. Even though they had a relatively easy regular-season schedule (opponents had only a .428 winning percentage), their playoff performance was outstanding.

As ESPN's John Clayton wrote last year, "The Ravens have that rare ability to reach into the chest of an opposing offense, remove its heart, squeeze it and return it to victims like a deflated football."

4. 1971 Minnesota Vikings
We were tempted to put the Vikings atop this list, just because they had one of the all-time best nicknames in sports history. "The Purple People Eaters" held their 1971 opponents to only 9.9 points per game, capping what might be the best three-year defensive run in NFL history. (In 1970, they gave up 10.2 ppg, and in 1969 9.5, the seventh and second-lowest totals in history; the 1971 team was fourth.) Considering that their motto was "Meet at the quarterback," it's no surprise that the Eaters held opposing QBs to a 40.4 rating, one of the lowest ever.

The Vikings, who went 11-3 before losing to the Cowboys in the divisional playoffs, shut out three opponents, and only one team scored more than 20 points against them. As a result, Alan Page became the first defensive player to ever be named NFL MVP. Carl Eller, Jim Marshall and safety Paul Krause joined Page on the All-Pro team.

5. 1962 Green Bay Packers
The great 1962 Packers had a rock-solid defense front to back, boasting an astounding five Hall of Famers: defensive linemen Willie Davis and Henry Jordan, linebacker Ray Nitschke, cornerback Herb Adderley, and safety Willie Wood. (For good measure, they also boasted a couple of other 1962 All-Pros in linebackers Dan Currie and Bill Forester.) Green Bay gave up just 10.8 points per game, shutting out opponents three times. The Packers held opposing QBs to a 43.5 rating, due, in part, to Wood's league-leading nine interceptions. The Packers defense allowed the Giants 291 yards in the NFL championship game, but held the Giants offense scoreless as the Packers won, 16-7 (New York scored on a blocked punt).

6. 1990 New York Giants

The Giants' Lawrence Taylor revolutionized the linebacker position.

The Giants allowed only 13.2 points a game against a very tough schedule -- they played against seven playoff teams during the regular season. Led by Hall of Fame linebacker Lawrence Taylor, New York's defense also came through in the playoffs, holding the Bears to just three points in the divisional playoff game. Then they allowed a tough 49ers offense just two field goals and one TD, and set up the game-winning score by forcing a late fumble to win the NFC title 15-13. In Super Bowl XXV, the Giant defense held its own against the Bills' no-huddle offense, and New York won 20-19.

"The Giants drove me crazy," said former Redskins coach Joe Gibbs. "They gave me the most fits. They were the opposite of Buddy Ryan's Bears defense. They played that soft two-deep zone that didn't allow any big plays. You had to earn everything you got against the Giants."

7. 1969 Kansas City Chiefs
The Super Bowl IV champion Chiefs boasted three future Hall of Famers on defense -- tackle Buck Buchanan and linebackers Bobby Bell and Willie Lanier -- and they earned their place on this list with a stellar postseason. But during the regular season, Hank Stram's "Triple Stack" defense, which gave the linebackers lots of room to roam, was superb, holding five opponents to fewer than 10 points and giving up an average of less than two touchdowns a game.

Then they got serious. Against the Super Bowl champion Jets in the AFL divisional playoff game at Shea Stadium, the Chiefs held on for a 13-6 victory, thanks to a remarkable three-play goal line stand that stifled the Jets on the one. After losing twice to the Raiders during the regular season, the Chiefs allowed a single touchdown, in the first quarter, to win the AFL title over Oakland 17-7. The Chiefs defense then stifled the Vikings in the Super Bowl, allowing only two rushing first downs and picking off three passes in the fourth quarter to win 23-7. Total points against the Chiefs in the playoffs: 20.

8. 1973 Miami Dolphins
The Dolphins 53/"No Name" Defense ("53" was linebacker Bob Matheson's number) held 11 opponents to 14 points or less, setting a record by allowing just 150 points in a 14-game season. Defensive end Bill Stanfill set a Dolphins' sack record that still stands, with 18.5. In the playoffs and Super Bowl, they allowed only 33 points against Cincinnati, Oakland and Minnesota. Stanfill, Manny Fernandez, Hall of Fame middle linebacker Nick Buoniconti, and safeties Dick Anderson (AP Defensive Player of the Year) and Jake Scott were all named to the 1973 All-Pro team.

Before facing the Dolphins in Super Bowl VIII, Vikings QB Fran Tarkenton oozed confidence, saying he'd solved the 53. "I think you've got to prepare for the 53 defense, you've got to make it so the Dolphins don't know what to expect. I'm sure we'll prepare a little bit different." It didn't work. The Vikings lost 24-7, scoring their only TD in the fourth quarter.

9. 1963 Chicago Bears
In 1963, Bears defensive coach George Allen came up with a new zone defense against the pass, befuddling opponents. With Doug Atkins and Ed O'Bradovich pressuring opposing QBs from their defensive end slots, and Bill George and Larry Morris defending against short passes from the linebacker position, the Bears picked off 36 passes, and allowed just 10.3 points and 227 yards per game. The Bears went on to win the NFL championship, thanks to the D. In the title game against Y.A. Tittle and the Giants, who had the best offense in the NFL, Chicago's five picks were the key, as the Bears won 14-10. George Allen got the game ball.

10. 1975 Los Angeles Rams
Fred Dryer. Jack Youngblood. Merlin Olson. Get the idea? They weren't the "Fearsome Foursome," but with those guys anchoring the defensive line, and All-Pros Isiah Robertson (linebacker) and Dave Elmendorf (safety), the Rams were almost impossible to score against. The Rams went 12-2, holding opponents to just 9.6 points a game, (the second-lowest average in NFL history) and ending the season with a six-game winning streak during which they gave up just 32 points. The defense wasn't as impressive in the postseason, surrendering 23 points in a first-round victory over the Cardinals before losing 37-23 to the Cowboys in the NFC title game.